A graphic display apparatus basically comprises a display screen, display controller, data channels and some input devices.
There are a lot of types of input devices one of which is an X-Y direction input device called "MAUSU" (tradename) configured to detect the moving direction and distance of a casing on a sheet.
The X-Y direction input device basically comprises a rotatably supported ball made of steel, for example, a first follower roller contacting and rotated by the ball, a second follower roller contacting and rotated by the ball and having an axis perpendicular to the axis of the first follower roller, first and second rotation detectors each including rotary electrical members such as a variable resistor and encoder to separately detect rotations of the first and second follower rollers, and a casing which receives and envelopes the ball, first and second follower rollers, first and second rotation detectors and other related members.
The casing has an aperture which opens at the bottom thereof to allow the ball to slightly project downward. When the casing is moved, rotating the ball along the sheet, the first and second follower rollers are rotated in predetermined different (X- and Y-) directions respectively. The amounts of rotation in the X- and Y-directions of the first and second follower rollers are detected by the first and second rotation detectors separately, as corresponding voltages or digital signals, and the signals are entered in the display apparatus.
The first and second rollers must be rotated in the casing, maintaining a perpendicular relationship between their axes. In the prior art arrangement, the rectangular relationship of the first and second follower rollers are established by previously fixing the follower rollers and first and second rotary electrical members in position of a frame and thereafter securing the frame to the casing by bolts.
Such an X-Y direction input device usually includes push switches to instruct deletion or dislocation of patterns displayed on the screen or to effect various signal processing for other switching and control operations. The push switch is fixed to a predetermined position of the casing by soldering it on a relatively hard switch board made of phenolic resin, for example, and thereafter securing the switch board to the casing by bolts. After the frame and switch board are secured to the casing, lead wires are soldered to lead terminals of the first and second rotary electrical members and terminals of the switch board to establish electrical connection therebetween.
Summarizing the prior art, assemblage of the X-Y direction input device is significantly complicated due to the bolt fixture of the frame and switch board to the casing and also due to subsequent soldering in a narrow space inside the casing for electrical connection.